The Thickness of Ice-Blocks. — Woodworth. 
281 
gravels and sands accumulated about its sides by the waters 
flowing past it and from its own surface, the melting of this 
upper ice, particularly if continued after the subsidence or 
diversion of other waters, would create a drainage channel 
leading awa} r from the side of the mass over the plain or 
kame-field to lower ground. 
I was led to conceive this proposition on observing that 
many of the ponds shown on the Massachusetts topographical 
atlas sheets, even where they have now no outlet, exhibit an 
old drainage furrow, often ten or more feet above the level of 
highest water in the pond, leading to a river system or to the 
sea. In January of this year, I was so fortunate as to see a 
miniature illustration of an ice-mass, with its attendant de- 
pression, and drainage furrow going forth from the lower side 
of the surrounding plain, on the gently sloping, sandy beach 
at Hull, Mass. On the same beach were other likewise minia- 
ture examples, in which the ice had disappeared and the water 
in the pit had shrunk below the level of the furrow. The ac- 
companying generalized contour-map will serve to illustrate 
these pits on the beach as well as the glacial ponds having a 
length of a mile or more. 
Generalized contoured map of a glacial lakelet, with drainage flume eroded by 
water from the ice standing above the level of the plain or surrounding drift deposits. 
Contour intervals from 10 to 20 ft. 
The following are instances cited from the region of (ape 
God : 
On the Wellfleet atlas sheet: Baker's pond and the Twin 
Cliff and Flat ponds have a distinct furrow or flume. 
On the Yarmouth sheet: Cedar pond has a furrow leading 
